Nomenclature

Stirling engines are frequently called by other names, including hot-air or hot-gas engines, or one of a number of designations reserved for particular arrangements of engine, i.e. I leinrici. Robinson, or Rankine-Napier. The result is a general lack of clarity in the nomenclature. It may be argued, convincingly, that the designation 'Stirling cycle' should be reserved for a particular idealized thermodynamic cycle, and the name 'Stirling engine' for a particular form of machine (which, incidentally, does not work on the Stilling cycle, a situation that does nothing to improve clarity). A preierred generic title would be 'regenerative thermal machine'. It is almost certainly too late for logic to prevail, and the name 'Stirling engine' will continue to be widely and indiscriminately used. 1 Iowcver, a clear distinction should always be made between machines where the flow is controlled by (a) volume changes (Stirling engines) and (b) valves (Ericsson engines), because they have radically different characteristics. In this work we are concerned principally with Stirling engines and take only passing note <>r Ericsson machines.

Use of the term 'Stirling engine' as the generic title for closed-form regenerative thermal engines is comparatively recent. It is believed to have originated al the Research Laboratories of Philips at Eindhoven about 1954 (Meijer 1978)1. Up to that time it was customary simply to refer

I Private communication: for other refcrcnccs, f-tc tlic tiibllogiaphy al ihe end of the liook for complete source details.

to hot-air engines and perhaps to preface this with the name of the inventor, i.e. Buckett, Wenham, Lehmann, Stirling, etc. The change of working fluid from aii to helium or hydrogen at Philips in the mid-fifties made the term 'hot-air engine' inappropriate. I he alternative title. 'Philips hot-gas engine' proved less attractive than 'Stirling engine1 and so this latter has passed into general usage.

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.